"""
Utilities related to formatting output or translating input.
"""
from __future__ import absolute_import

from string import Formatter
from rez.vendor.enum import Enum
from rez.vendor.version.requirement import Requirement
from rez.exceptions import PackageRequestError
from pprint import pformat
import os
import os.path
import re
import time


PACKAGE_NAME_REGSTR = "[a-zA-Z_0-9](\.?[a-zA-Z0-9_]+)*"
PACKAGE_NAME_REGEX = re.compile(r"^%s\Z" % PACKAGE_NAME_REGSTR)

ENV_VAR_REGSTR = r'\$(\w+|\{[^}]*\})'
ENV_VAR_REGEX = re.compile(ENV_VAR_REGSTR)

FORMAT_VAR_REGSTR = "{(?P<var>.+?)}"
FORMAT_VAR_REGEX = re.compile(FORMAT_VAR_REGSTR)

# package names that are invalid because they may clash with reserved dir
# names in some package repos (eg filesystem)
#
invalid_package_names = (
    "__pycache__",
)


def is_valid_package_name(name, raise_error=False):
    """Test the validity of a package name string.

    Args:
        name (str): Name to test.
        raise_error (bool): If True, raise an exception on failure

    Returns:
        bool.
    """
    is_valid = (
        PACKAGE_NAME_REGEX.match(name) and
        name not in invalid_package_names
    )

    if raise_error and not is_valid:
        raise PackageRequestError("Not a valid package name: %r" % name)
    return is_valid


class PackageRequest(Requirement):
    """A package request parser.

    Example:

        >>> pr = PackageRequest("foo-1.3+")
        >>> print(pr.name, pr.range)
        foo 1.3+
    """
    def __init__(self, s):
        super(PackageRequest, self).__init__(s)
        is_valid_package_name(self.name, True)


class StringFormatType(Enum):
    """Behaviour of key expansion when using `ObjectStringFormatter`."""
    error = 1  # raise exception on unknown key
    empty = 2  # expand to empty on unknown key
    unchanged = 3  # leave string unchanged on unknown key


class ObjectStringFormatter(Formatter):
    """String formatter for objects.

    This formatter will expand any reference to an object's attributes.
    """
    error = StringFormatType.error
    empty = StringFormatType.empty
    unchanged = StringFormatType.unchanged

    def __init__(self, instance, pretty=False, expand=StringFormatType.error):
        """Create a formatter.

        Args:
            instance: The object to format with.
            pretty: If True, references to non-string attributes such as lists
                are converted to basic form, with characters such as brackets
                and parentheses removed.
            expand: `StringFormatType`.
        """
        self.instance = instance
        self.pretty = pretty
        self.expand = expand

    def convert_field(self, value, conversion):
        if self.pretty:
            if value is None:
                return ''
            elif isinstance(value, list):
                def _str(x):
                    if isinstance(x, unicode):
                        return x
                    else:
                        return str(x)

                return ' '.join(map(_str, value))

        return Formatter.convert_field(self, value, conversion)

    def get_field(self, field_name, args, kwargs):
        if self.expand == StringFormatType.error:
            return Formatter.get_field(self, field_name, args, kwargs)
        try:
            return Formatter.get_field(self, field_name, args, kwargs)
        except (AttributeError, KeyError, TypeError):
            reg = re.compile("[^\.\[]+")
            try:
                key = reg.match(field_name).group()
            except:
                key = field_name
            if self.expand == StringFormatType.empty:
                return ('', key)
            else:  # StringFormatType.unchanged
                return ("{%s}" % field_name, key)

    def get_value(self, key, args, kwds):
        if isinstance(key, str):
            if key:
                try:
                    # Check explicitly passed arguments first
                    return kwds[key]
                except KeyError:
                    pass

                try:
                    # we deliberately do not call hasattr() first - hasattr()
                    # silently catches exceptions from properties.
                    return getattr(self.instance, key)
                except AttributeError:
                    pass

                return self.instance[key]
            else:
                raise ValueError("zero length field name in format")
        else:
            return Formatter.get_value(self, key, args, kwds)


class StringFormatMixin(object):
    """Turn any object into a string formatter.

    An object inheriting this mixin will have a `format` function added, that is
    able to format using attributes of the object.
    """
    format_expand = StringFormatType.error
    format_pretty = True

    def format(self, s, pretty=None, expand=None):
        """Format a string.

        Args:
            s (str): String to format, eg "hello {name}"
            pretty (bool): If True, references to non-string attributes such as
                lists are converted to basic form, with characters such as
                brackets and parenthesis removed. If None, defaults to the
                object's 'format_pretty' attribute.
            expand (`StringFormatType`): Expansion mode. If None, will default
                to the object's 'format_expand' attribute.

        Returns:
            The formatting string.
        """
        if pretty is None:
            pretty = self.format_pretty
        if expand is None:
            expand = self.format_expand

        formatter = ObjectStringFormatter(self, pretty=pretty, expand=expand)
        return formatter.format(s)


def expand_abbreviations(txt, fields):
    """Expand abbreviations in a format string.

    If an abbreviation does not match a field, or matches multiple fields, it
    is left unchanged.

    Example:

        >>> fields = ("hey", "there", "dude")
        >>> expand_abbreviations("hello {d}", fields)
        'hello dude'

    Args:
        txt (str): Format string.
        fields (list of str): Fields to expand to.

    Returns:
        Expanded string.
    """
    def _expand(matchobj):
        s = matchobj.group("var")
        if s not in fields:
            matches = [x for x in fields if x.startswith(s)]
            if len(matches) == 1:
                s = matches[0]
        return "{%s}" % s
    return re.sub(FORMAT_VAR_REGEX, _expand, txt)


def expandvars(text, environ=None):
    """Expand shell variables of form $var and ${var}.

    Unknown variables are left unchanged.

    Args:
        text (str): String to expand.
        environ (dict): Environ dict to use for expansions, defaults to
            os.environ.

    Returns:
        The expanded string.
    """
    if '$' not in text:
        return text

    i = 0
    if environ is None:
        environ = os.environ

    while True:
        m = ENV_VAR_REGEX.search(text, i)
        if not m:
            break
        i, j = m.span(0)
        name = m.group(1)
        if name.startswith('{') and name.endswith('}'):
            name = name[1:-1]
        if name in environ:
            tail = text[j:]
            text = text[:i] + environ[name]
            i = len(text)
            text += tail
        else:
            i = j
    return text


def indent(txt):
    """Indent the given text by 4 spaces."""
    lines = (("    " + x) for x in txt.split('\n'))
    return '\n'.join(lines)


def dict_to_attributes_code(dict_):
    """Given a nested dict, generate a python code equivalent.

    Example:
        >>> d = {'foo': 'bah', 'colors': {'red': 1, 'blue': 2}}
        >>> print(dict_to_attributes_code(d))
        foo = 'bah'
        colors.red = 1
        colors.blue = 2

    Returns:
        str.
    """
    lines = []
    for key, value in dict_.items():
        if isinstance(value, dict):
            txt = dict_to_attributes_code(value)
            lines_ = txt.split('\n')
            for line in lines_:
                if not line.startswith(' '):
                    line = "%s.%s" % (key, line)
                lines.append(line)
        else:
            value_txt = pformat(value)
            if '\n' in value_txt:
                lines.append("%s = \\" % key)
                value_txt = indent(value_txt)
                lines.extend(value_txt.split('\n'))
            else:
                line = "%s = %s" % (key, value_txt)
                lines.append(line)

    return '\n'.join(lines)


def columnise(rows, padding=2):
    """Print rows of entries in aligned columns."""
    strs = []
    maxwidths = {}

    for row in rows:
        for i, e in enumerate(row):
            se = str(e)
            nse = len(se)
            w = maxwidths.get(i, -1)
            if nse > w:
                maxwidths[i] = nse

    for row in rows:
        s = ''
        for i, e in enumerate(row):
            se = str(e)
            if i < len(row) - 1:
                n = maxwidths[i] + padding - len(se)
                se += ' ' * n
            s += se
        strs.append(s)
    return strs


def print_colored_columns(printer, rows, padding=2):
    """Like `columnise`, but with colored rows.

    Args:
        printer (`colorize.Printer`): Printer object.

    Note:
        The last entry in each row is the row color, or None for no coloring.
    """
    rows_ = [x[:-1] for x in rows]
    colors = [x[-1] for x in rows]
    for col, line in zip(colors, columnise(rows_, padding=padding)):
        printer(line, col)


time_divs = (
    (365 * 24 * 3600, "years", 10),
    (30 * 24 * 3600, "months", 12),
    (7 * 24 * 3600, "weeks", 5),
    (24 * 3600, "days", 7),
    (3600, "hours", 10),
    (60, "minutes", 10),
    (1, "seconds", 60))


def readable_time_duration(secs):
    """Convert number of seconds into human readable form, eg '3.2 hours'.
    """
    return _readable_units(secs, time_divs, True)


memory_divs = (
    (1024 * 1024 * 1024 * 1024, "Tb", 128),
    (1024 * 1024 * 1024, "Gb", 64),
    (1024 * 1024, "Mb", 32),
    (1024, "Kb", 16),
    (1, "bytes", 1024))


def readable_memory_size(bytes_):
    """Convert number of bytes into human readable form, eg '1.2 Kb'.
    """
    return _readable_units(bytes_, memory_divs)


def _readable_units(value, divs, plural_aware=False):
    if value == 0:
        unit = divs[-1][1]
        return "0 %s" % unit
    neg = (value < 0)
    if neg:
        value = -value

    for quantity, unit, threshold in divs:
        if value >= quantity:
            f = value / float(quantity)
            rounding = 0 if f > threshold else 1
            f = round(f, rounding)
            f = int(f * 10) / 10.0
            if plural_aware and f == 1.0:
                unit = unit[:-1]
            txt = "%g %s" % (f, unit)
            break

    if neg:
        txt = '-' + txt
    return txt


def get_epoch_time_from_str(s):
    """Convert a string into epoch time. Examples of valid strings:

        1418350671  # already epoch time
        -12s        # 12 seconds ago
        -5.4m       # 5.4 minutes ago
    """
    try:
        return int(s)
    except:
        pass

    try:
        if s.startswith('-'):
            chars = {'d': 24 * 60 * 60,
                     'h': 60 * 60,
                     'm': 60,
                     's': 1}
            m = chars.get(s[-1])
            if m:
                n = float(s[1:-1])
                secs = int(n * m)
                now = int(time.time())
                return max((now - secs), 0)
    except:
        pass

    raise ValueError("'%s' is an unrecognised time format." % s)


positional_suffix = ("th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th")


def positional_number_string(n):
    """Print the position string equivalent of a positive integer. Examples:

        0: zeroeth
        1: first
        2: second
        14: 14th
        21: 21st
    """
    if n > 20:
        suffix = positional_suffix[n % 10]
        return "%d%s" % (n, suffix)
    elif n > 3:
        return "%dth" % n
    elif n == 3:
        return "third"
    elif n == 2:
        return "second"
    elif n == 1:
        return "first"
    return "zeroeth"


# regex used to expand user; set here to avoid recompile on every call
EXPANDUSER_RE = re.compile(
    r'(\A|\s|[{pathseps}])~([{seps}]|[{pathseps}]|\s|\Z)'.format(
    seps = re.escape(''.join(set([os.sep + (getattr(os, 'altsep') or os.sep)]))),
    pathseps = re.escape(''.join(set([os.pathsep + ';'])))))


def expanduser(path):
    """Expand '~' to home directory in the given string.

    Note that this function deliberately differs from the builtin
    os.path.expanduser() on Linux systems, which expands strings such as
    '~sclaus' to that user's homedir. This is problematic in rez because the
    string '~packagename' may inadvertently convert to a homedir, if a package
    happens to match a username.
    """
    if '~' not in path:
        return path

    if os.name == "nt":
        if 'HOME' in os.environ:
            userhome = os.environ['HOME']
        elif 'USERPROFILE' in os.environ:
            userhome = os.environ['USERPROFILE']
        elif 'HOMEPATH' in os.environ:
            drive = os.environ.get('HOMEDRIVE', '')
            userhome = os.path.join(drive, os.environ['HOMEPATH'])
        else:
            return path
    else:
        userhome = os.path.expanduser('~')

    def _expanduser(path):
        return EXPANDUSER_RE.sub(
            lambda m: m.groups()[0] + userhome + m.groups()[1],
            path)

    # only replace '~' if it's at start of string or is preceeded by pathsep or
    # ';' or whitespace; AND, is followed either by sep, pathsep, ';', ' ' or
    # end-of-string.
    #
    return os.path.normpath(_expanduser(path))


def as_block_string(txt):
    """Return a string formatted as a python block comment string, like the one
    you're currently reading. Special characters are escaped if necessary.
    """
    import json

    lines = []
    for line in txt.split('\n'):
        line_ = json.dumps(line)
        line_ = line_[1:-1].rstrip()  # drop double quotes
        lines.append(line_)

    return '"""\n%s\n"""' % '\n'.join(lines)


_header_br = '#' * 80
_header_br_minor = '-' * 80


def header_comment(executor, txt):
    """Convenience for creating header-like comment in a rex executor.

    Args:
        executor (`RexExecutor`): Executor.
        txt (str): Comment text.
    """
    executor.comment("")
    executor.comment("")
    executor.comment(_header_br)
    executor.comment(txt)
    executor.comment(_header_br)


def minor_header_comment(executor, txt):
    executor.comment("")
    executor.comment(txt)
    executor.comment(_header_br_minor)


# Copyright 2013-2016 Allan Johns.
#
# This library is free software: you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation, either
# version 3 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
